Cruise Control

Downhill running has its upsides but kills your quads. Here's how to avoid the burn.

Six weeks before the 2006 Chicago Marathon, Benjamin Gailey ran in a relay in the Rocky Mountains as a tune-up. He chose two downhill legs, which dropped 1,900 feet each, figuring they'd be easy and let him save his strength for the marathon. Big mistake.

"I couldn't even walk afterward," says Gailey, 31. He went to Chicago hoping to qualify for the Olympic Trials, but his 2:37 finishing time was too slow by 15 minutes. "The downhills definitely took a toll," he says. "I just didn't have the strength that I should have."

Gailey learned the hard way: As fun as it can be to fly down a hill with the help of gravity's pull, steep descents can zap the power you need to take on flat stretches and uphill climbs, and leave your quads feeling trashed for days afterward. "Everyone underestimates downhills, generally because they don't present much of a challenge to negotiate," says coach and exercise physiologist Jack Daniels, Ph. D. "But they can leave your running muscles pretty stressed out."

Why is that? Running downhill requires the muscles to lengthen, or make eccentric muscle contractions, which can cause microscopic tears in the muscle fibers and generate more force than when you're running uphill or on flat ground. To make matters worse: It's easy to hit top speed on a steep descent—and the faster you move, the harder each foot strikes the ground, and the more pounding the muscles endure.

That doesn't mean you should avoid all downward slopes. In fact, research has shown that running downhills can give your pace a lift. A 2006 study published in the Journal of Strength and Conditioning Research showed that when sprinters trained on uphills and downhills, they improved speed and foot turnover more than running uphills or flat surfaces alone. By incorporating downhills into your training, you can weather them better and bounce back from them sooner.

Start Small

Add downhills to your routine a little at a time, says Daniels. Start with a short, gradual slope, with a two-to three-percent grade, and move on to steeper and longer descents as you get more comfortable. At first, run on a gentler surface, such as grass, then move on to roads. Treat downhill workouts as hard sessions, and follow them with two or three days of easy running. And be sure to back off of downhills in the two weeks or so before a target race, he adds. Because your body absorbs a bigger impact with each footstrike, you could be at risk for IT band syndrome and other injuries, cautions Irene Davis, Ph. D, director of the Running Injury Clinic at the University of Delaware. "If you're running on a more compliant surface and a less steep grade, that will help lessen the impact," she says.